| Popis: |
Cross-contamination is one of the main pathways by which pathogens enter, survive, and grow in the foods we consume. To address this issue, a tried and proven method is the use of antimicrobial packaging materials that could inactivate microorganisms. Quaternary ammonium compounds (QACs) were documented to be effective against Gram-positive and negative bacteria, enveloped and non-enveloped viruses, and can be used as coating materials on stainless-steel surfaces. This dissertation reports on studies done on dry and wet abrasion testing of a silane QAC antimicrobial coating on a stainless-steel substrate using the contact-based approach. The first part of this dissertation (Chapter 3) studied the resilience of the coating material (first and second applications) to repeated dry abrasions while still maintaining its antimicrobial efficacy to Listeria innocua and Escherichia Coli K12 (L. innocua and E. coli K12), as well as the physio-chemical changes to the coatings during dry abrasions. The antimicrobial performances of the coating were tested by inoculating bacteria on the coated surfaces before and after dry rubbings. Physio-chemical changes to the coating were determined using SEM/EDS analysis (Scanning electron microscopy and energy dispersive X-ray spectroscopy). The results showed that the coating inactivated L. innocua and E. coli K12 after 60 and 120 rub cycles, respectively. A second application of the coating, after the first coating was removed by dry abrasion, gave the stainless-steel a similar inactivation ability against L. innocua when compared with the first coating. The SEM/EDS analysis showed a decline in the carbon, oxygen, silicon, and chlorine compositions in the coated surface after 120 rub cycles. This provided information about how the dry abrasion degraded the coating.The second part of this dissertation (Chapter 4) evaluated the resilience of the coating material to repeated wet abrasions with an industrial detergent and how many washing cycles were required to remove the antibacterial ability of the coating to L. innocua and E. coli K12. This chapter also investigated how the physio-chemical properties of the coatings were affected by the wet abrasions. The methods to investigated these were similar to the approaches used in Chapter 3. The results showed that the coating was able to inactivate L. innocua and E. coli K12 after 40 and 10 wash cycles, respectively. The SEM/EDS analysis showed the mass fractions of carbon and silicon in the 40-wash cycle samples were similar to the levels of the non-coated sample, indicating that the coating was mostly removed by the detergent. The third part of this dissertation (Chapter 5) investigated the resilience of the coating material to repeated dry abrasions while still maintaining its antivirus efficacy to the non-enveloped Human Rotavirus A (RVA) and enveloped Porcine Respiratory Coronavirus (PRCV). This was determined by using cell culture immunofluorescence (CCIF) and quantitative reverse transcription-PCR (qRT-PCR) to examine the viruses’ titers after they were exposed for 24 hours to the coated surfaces before and after dry abrasions. The CCIF results showed that the coating was virucidal to RVA and PRCV after 150 rub cycles, but the RVA was more sensitive to the coating when compared with the PRCV. When the qRT-PCR method was used, the results showed a lower level of log reductions for both the RVA and PRCV except for the PRCV on the 0-rub coated sample when the result showed that there was a 2 log FFU/ml reduction.This study confirmed the potential of this silane QAC coating for use on frequently washed stainless-steel surfaces, such as food preparation surfaces, or on high touch surfaces such as door and window handles, as examples, to reduce the risk of cross-contamination and the spreading of food-borne diseases. |
